ML110600717

Email Request for Additional Information, Round 2, Nrr/Dci/Cvib Review, Amendment Request for Extended Power Uprate to Increase the Maximum Reactor Core Power Operating Limit from 3898 to 4408 Mwt

ML110600717
Person / Time
Site:	Grand Gulf
Issue date:	03/01/2011
From:	Wang A Plant Licensing Branch IV
To:	Burford J, Millar D, Wang A Entergy Operations, Plant Licensing Branch IV
Wang, A B, NRR/DORL/LPLIV, 415-1445
References
TAC ME4679
Download: ML110600717 (5)

Text

From:

Wang, Alan Sent:

Tuesday, March 01, 2011 10:54 AM To:

Wang, Alan; MILLAR, DANA; 'Jerry Burford' Cc:

Lent, Susan; Burkhardt, Janet

Subject:

GG EPU Containment and Ventilation Branch Request for Additional Information (ME4679)

Dana and Jerry, By letter dated September 8, 2010 (Agencywide Documents Access and Management System, Accession No. ML1002660403), Entergy Operations, Inc. (Entergy, the licensee), submitted a request to amend the Facility Operating License No. NPF-29 for Grand Gulf Nuclear Station, Unit 1 (GGNS). The licensee proposed a license amendment request (LAR) for an extended power uprate (EPU) to increase the maximum reactor core power operating limit from 3898 megawatts thermal (MWt) to 4408 MWt. The U.S. Nuclear Regulatory Commission (NRC) staff has determined that the following additional information is needed for the NRC staff to complete our review of this amendment. This request for additional information (RAI) was discussed with Mr. Jerry Burford of your staff on March 1, 2011, and it was agreed that a response would be provided within 30 days of receipt of this E-mail. If circumstances result in the need to revise the requested response date, please contact me at (301) 415-1445 or via e-mail at Alan.Wang@nrc.gov.

The following RAIs are related to the Containment and Ventilation Branch portion of the LAR review. As previously discussed if the information for Question 1 could be provided as soon as possible it would help in our review.

RAIs on PUSAR Section 2.6

1. The following information is needed to perform our confirmatory analysis:

(a) Location of the main steam flow limiter relative to the reactor vessel.

(b) Break area for main steam line break for short term analysis.

(c) Is the feedwater mass and energy input to the reactor for short term analysis the same as given in NEDC-33477P Revision 0, Table 2.6-2 item 8. In case different values were used please provide reasons.

(d) PUSAR Table 2.6-2, items 2b, 2c, 2d, 3a, 3d, 3e, and 3f, please specify which input values from the given range were used for the various long term analyses i.e. for design basis accident (DBA) loss of coolant accident (LOCA) for containment response, DBA LOCA for NPSH, Appendix R Fire, station blackout (SBO), and anticipated transient without scram (ATWS).

(e) PUSAR Table 2.6-2, item 5a, explain the reasons for variation of the RHR heat exchanger K-value for different modes.

2. Section 2.6.5.2 specifies the runout pump flow rate for residual heat removal (RHR) pump as 8,940 gpm, and runout flow rate for low pressure core spray (LPCS) pump as 9,100 gpm.

Table 2.6-2 specifies low pressure coolant injection (LPCI) pump (which is the RHR pump) runout flow rate of 6600 gpm, and LPCS pump runout flow rate of 7000 gpm. Please clarify or correct the discrepancy.

3. Regarding PUSAR Section 2.6.5.2, for the required net positive suction head (NPSH) of the pumps, please provide the following information:

(a) Provide the basis of the values of the required NPSH that were used to compare with the available NPSH for the RHR, LPCS, and HPCS pumps.

(b) What uncertainties were included in the evaluation of the required NPSH from the data provided by the vendor?

4. Regarding PUSAR Section 2.6.1, third and fourth paragraphs under Technical Evaluation, please clarify the following:

The third paragraph states that M3CPT code was used to model the short-term containment pressure and temperature response. The fourth paragraph refers to LAMB computer code, but does not explicitly state that it was used for determining the extended power uprate (EPU) reactor vessel break flow for input to the M3CPT code. Please clarify whether LAMB computer code was used for mass and energy release input to M3CPT code or only M3CPT code was used to model both reactor and containment for short term response.

5. Please state the assumptions and input conditions for short term containment pressure and temperature analysis and provide a comparison with the assumptions and inputs with the current licensing basis (CLB) analysis. Provide justifications for any variation of the proposed assumptions and input condition from those in the CLB analysis

6. Grand Gulf Nuclear Station Unit 1 (GGNS) updated final safety analysis report (UFSAR)

Sections 6.2.1.1.5.4 and 6.2.1.1.5.5 provides results and assumptions of current licensing basis (CLB) steam bypass capability analysis without sprays and heat sinks and with sprays and heat sinks respectively for small reactor system breaks. Provide a table comparing the assumptions and results of the CLB and the EPU analysis including justification of differences in assumptions used in the EPU analysis.

7. PUSAR Section 2.6.1.2.1 states that the containment dynamic loads are based on the short term DBA LOCA analysis for RSLB. However the load analysis for condensation oscillation and chugging which occurs in the long term is not described. Provide a description of the most limiting containment analyses which resulted in a response showing that it (the response) is bounded by the conditions used to define the condensation oscillation and chugging loads.

8. Describe the EPU analysis and its results that determined the effect of vent clearing pressure, condensation oscillation pressure and chugging pressure on the weir wall.

Provide their comparison with the results for the CLB analysis.

9. Regarding PUSAR Section 2.6.1.2.2; describe the analysis which demonstrated the low-low-set (LLS) SRV setpoint logic successfully prevented subsequent actuations of multiple valves. Also describe the analysis that demonstrated the time between successive actuation of SRV is long enough that water in the discharge line returns to its pre-actuation or lower than pre-actuation level.

10. GGNS UFSAR Revision 5 Section 6.2.1.2.3, Design Evaluation, states that the subcompartment analysis was performed using Bechtel computer program COPDA, as

described in Bechtel topical report BN-TOP-4, Rev 1. PUSAR Section 2.6.2 under heading Subcompartment Pressurization Evaluation, states original design basis annulus pressurization analysis is based on mass and energy release rates generated using the instantaneous break NEDO-24548 methodology which is not documented in GGNS UFSAR.

Please provide the following information:

(a) The topical reports which describe the methodologies used for current and proposed subcompartment mass and energy release and pressurization analysis. In case the PUSAR and UFSAR are in conflict please clarify or correct.

(b) Differences in assumptions and justification of differences between the current and the proposed licensing basis methodologies for subcompartment mass and energy and pressurization calculations.

11. PUSAR Section 2.6.2 under heading Subcompartment Pressurization Evaluation, states:

Because of issues identified in SC 09-01 the simplistic instantaneous break NEDO-24548 mass and energy release methodology was judged to be potentially non-conservative as the method could potentially result in artificial shifts of the pressure response frequency content. Please describe the issues that makes the NEDO-24548 methodology non-conservative.

12. PUSAR Section 2.6.2 under heading Break Flow Analysis states: The TRACG model used for the EPU evaluation provides a better estimate of the mass and energy releases resulting from breaks in the recirculation suction, recirculation discharge, and FW lines. The use of TRACG mass and energy release allows the effect of alternate operating conditions to be realistically predicted.

(a) Describe what is meant by better estimate of mass and energy estimate in terms uncertainty in the current methodology and the TRACG calculation.

(b) Provide explanation of: The use of TRACG mass and energy release allows the effect of alternate operating conditions to be realistically predicted.

13. PUSAR Table 2.6-1 Note 7 states The current design limit for the bulk suppression pool temperature is 185 degrees Fahrenheit (oF). For EPU implementation, this design limit has been increased to 210°F. Please describe the impact on environmental qualification of safety related systems, structures, and components (SSCs) due to this change.

14. Refer to Section 2.6.2, under heading Annulus Pressurization third paragraph, please explain why maintaining the cell aspect ratio approximately one (1) will ensure the nodalization will not distort the acoustic wave propagation?

15. PUSAR Table 2.6-1 states the peak containment temperature for DBA LOCA EPU-with EPU Model is 142°F. PUSAR Section 2.6.3.1.1, second paragraph states Table 2.6-1 shows the calculated WW gas space temperature of 142°F for the DBA LOCA at EPU. Explain and/or clarify the difference between containment and wetwell?

16. Regarding PUSAR Section 2.6.5.1, third paragraph and last sentence; explain what is meant by ECCS NPSH pump limit of 194°F?

17. Regarding PUSAR Section 2.6.5.1, third paragraph, what is the limiting value of available NPSH at 189°F and the limiting values of the required NPSH (including uncertainties) for the ECCS pumps during the EPU DBA-LOCA event.

18. Regarding PUSAR Section 2.6.5.1, fourth paragraph, what are the values of available NPSH at 198°F and the required NPSH (including uncertainties) for the RHR pump during the non-ASDC event. Provide a comparison with the current values of available and required NPSH for this event.

19. Regarding PUSAR Table 2.6-3, at the peak bulk suppression pool temperature for the three events stated in this table; provide the limiting value of available NPSH and the limiting value of required NPSH for the ECCS pumps used during these events. Provide a comparison with the current values of available and required NPSH for these events.

20. Regarding PUSAR Section 2.6.5.2, first paragraph states that no change in the suppression pool temperature results from the implementation of EPU. This statement is in conflict with the results given in Table 2.6-1 which gives the peak suppression pool temperature for EPU DBA LOCA as 189°F compared to the current value of 181°F, resulting in a reduced NPSH margin. Provide an explanation for the differences in the statements. By how much would the NPSH margin be reduced with EPU implementation?

21. Regarding PUSAR Section 2.6.6; provide an evaluation of the effect of increased secondary containment heat load due to EPU on the drawdown time and offsite dose.

22. PUSAR Section 2.6.6 last paragraph states The secondary containment temperature and pressure are not evaluated further in the CLTR because there is no effect as result of EPU.

Provide an explanation as to why the secondary containment temperature and pressure are not affected due to increased heat load in the secondary containment.

23. Regarding PUSAR Table 2.6-1, explain why the peak drywell to containment differential pressure for the analysis of record (AOR) is due to MSLB (per footnote number 2 for table 6.2-1), whereas for the EPU analysis method with CLTP assumptions and for the EPU analysis is due to RSLB (per footnote number 4 for Table 2.6-1).

24. Regarding PUSAR Table 2.6-1, provide reasons why the results of containment analysis for DBA LOCA at CLTP from AOR (column number 2 of Table 2.6-1) are different from DBA LOCA at CLTP with EPU model (column number 3 of Table 2.6-1).

25. Regarding PUSAR Table 2.6-1, please confirm that the 10 CFR 50 Appendix J containment integrated leak rate test pressure would be based on the short term peak pressure of 14.8 psig.

26. As indicated in Section 2.6.1 of NEDC-33477, EPU implementation at GGNS requires the evaluation of the containment pressure and temperature response due to increased decay heat resulting from EPU implementation. However, there is no discussion regarding the effects of the suppression pool (SP) temperature increase on the structural integrity of the containment structures, including the wetwell (WW) and drywell (DW). Please discuss the impact of the revised suppression pool limit (from 185oF to 210 oF) on the structural integrity of the containment structures. Specifically, please address the effects of the temperature rise on the design basis requirements related to the structural evaluation of the containment, including a discussion of the effects on the design basis loading combinations and whether the associated stress limits are satisfied following EPU implementation.

RAI on PUSAR Section 2.7

27. PUSAR Section 2.7.3 under heading Technical Evaluation states that EPU does not add any electrical or electrical equipment to the control room. Please state whether any existing equipment will be altered that would increase the control room heat load. If so, provide an evaluation of the of the control room area ventilation system (CRAVS) under the increased heat load due to equipment alteration.